||The present research work was carried out to investigate the in vitro antioxidant activity of methanolic extracts of the whole plant of Glinus oppositifolius (MEGO) and leaves of Sesbania grandiflora (MESG). The therapeutic effects of tannins and flavonoids can be largely attributed to their antioxidant properties. The quantitative estimation of phenolic content was measured by using UV-spectrophotometric method. The total phenolic content value of MEGO was 12.2±0.12w/w and of MESG was 8.34±0.08 % w/w, respectively, and total flavonoid estimation of MEGO and MESG showed the content values of 4.9±0.02 % w/w and 1.2±0.13 %w/w, respectively, for quercetin and 3.6±0.18 % w/w and 1.56±0.09 % w/w, respectively, for rutin. The results revealed that these plants have antioxidant activity. The antioxidant activity of MEGO was found to be more potent than MESG. So finally it indicates that both the plants contains antioxidant substances which can be used for the treatment of oxidative stress related diseases.